Anxiety or Stress: Tachycardia can be a common response to anxiety or stress, which may be heightened during pregnancy due to concerns about the health of the fetus or the upcoming birth.

Dehydration: Mild dehydration can lead to tachycardia, and pregnant women may be more susceptible due to increased blood volume and changes in cardiovascular dynamics.
Anemia: Common in pregnancy due to increased blood volume and demand for iron, anemia can cause tachycardia as the body attempts to compensate for reduced oxygen delivery to tissues.
Thyroid Disorders: Both hyperthyroidism and hypothyroidism can occur during pregnancy, with hyperthyroidism more likely to cause tachycardia due to the increased metabolic rate.

Pulmonary Embolism (PE): Although less common, PE is a life-threatening condition that requires immediate attention. Pregnancy increases the risk of PE due to venous stasis and hypercoagulability.
Cardiac Conditions (e.g., Mitral Stenosis, Cardiomyopathy): Pre-existing cardiac conditions can worsen during pregnancy due to increased blood volume and cardiac output demands, leading to symptoms like tachycardia.
Preeclampsia: A condition characterized by high blood pressure and often protein in the urine, preeclampsia can lead to tachycardia among other symptoms and is a significant risk to both mother and fetus if not promptly treated.

Hyperparathyroidism: Although rare, hyperparathyroidism can cause hypercalcemia, leading to tachycardia among other symptoms.
Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of tachycardia, hypertension, and other symptoms due to excessive catecholamine release.
Thyroid Storm: A life-threatening complication of untreated or undertreated hyperthyroidism, characterized by severe tachycardia, fever, and other systemic symptoms.